Background: Oncotype Dx is a 21-gene recurrence score, which is used as a diagnostic tool for the recurrence of breast cancer. It is also used to determine the benefit of chemotherapy for breast cancer in early stages. This study investigates the relationship of Oncotype Dx with pathological prognostic markers of protein Ki 67, Nottingham Prognostic Index (NPI) and tumor grade.
Methods: Data for early breast cancer patients treated at our tertiary care center was collected for statistical analysis. Data for patients from 2014 to 2018 was recorded for patient's age, ER/PR status, Ki 67, nodal status, tumor grade, NPI along with Oncotype Dx score. Metric measurements were described as mean ± SD and the non-metric data was represented by frequency (%). Chi-square or Fisher's exact tests as well as logistic regression was applied to assess the associations at 95% CI.
Results: Among 156 breast cancer patients, the mean age was 55.7 ± 9.4 years. The tumors were classified into Grade-I (12.8%), Grade-II (67.3%) and Grade-III (19.9%). Ki67 score was 12.8 ± 12.0 and NPI score was 3.7 ± 0.8. The mean Oncotype Dx score was 17.0 ± 9.1; it was 14.1 ± 6.8 for Grade-I tumors; 15.7 ± 7.5 for grade -II tumors; and 23.2 ± 12.3 for grade-III tumors [Mean Oncotype Dx score across Tumor grades was compared by ANOVA (η = 0.121), p < 0.001]. While logistic regression analyses for the dichotomized Oncotype Dx higher score (≥25) was significantly associated with grade-III tumors odds ratio (OR) = 13.72 (95% CI: 1.62-115.89), higher Ki67 (>20) OR = 14.40, (95% CI: 1.44-143.71), average NPI score (2.41-3.40), OR = 13.60, (95% CI: 1.57-117.94) to poor NPI (>5.4). The association of Oncotype Dx with age, tumor size and nodal status was statistically not significant.
Conclusions: This study revealed that age, Ki67, tumor size and nodal status did not have a statistically significant impact on Oncotypye Dx recurrence score in the targeted patient population. There was a significant correlation of low grade node negative patients with Oncotype Dx while high grade node negative patients had poor correlations with Oncotype Dx. The use of Oncotype Dx has shown to be less cost-effective and has no noticeable association with improved life expectancy in the targeted patient population (i.e., hormone positive, node negative cases) in comparison with current clinical practices in Saudi Arabia and it is less likely to be cost-effective in this group of patients.
Keywords: Adjuvant chemotherapy; Ki67; Nottingham Prognostic Index; Oncotype Dx Recurrence Score.
Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.